1. Field of the Invention
The present invention relates to conductive paste compositions and ceramic substrates. More particularly, the present invention relates to application of a conductive paste composition comprising gold powder, crystallized glass frit, etc. to a ceramic substrate to obtain a highly reliable ceramic substrate, whereby formation of cracks is minimized.
2. Discussion of Background
Gold-containing conductive pastes for ceramic substrates which have been practically employed, are designed so that they are applied on ceramic substrates made of e.g. alumina, which have been fired and solidified beforehand, and then they are fired. Therefore, they have problems such that when they are printed on green sheets and fired simultaneously therewith, cracking or peeling is likely to result in the formed conductors, or the glass frit contained in the pastes tends to cover and glaze the conductor surface, whereby the solderability of the conductors tends to be poor.
Further, glass frit contained in the conductive pastes is likely to be softened prior to the complete decomposition of an organic binder in the green sheets and thus hinder the dispersion of the decomposed gas, whereby there will be a problem of blistering i.e. a phenomenon wherein the conductor surface swells like a balloon by the pressure of the decomposed gas, or a drawback that the adhesion of the conductors to the ceramic substrates tends to be poor.
Further, when the conventional conductive pastes are used as internal conductors of multi-layered ceramic substrates, it is likely that glass frit contained in the conductive pastes tends to glaze before the complete decomposition of the organic binder and thus hinder the dispersion of the decomposition gas, whereby blistering i.e. a phenomenon wherein the multi-layered ceramic substrate on the conductor swells like a balloon, is likely to take place. Further, there is a problem that the adhesion between the conductor and the multi-layered ceramic substrate is inadequate, whereby there will be delamination i.e. a phenomenon in which a void space is formed at the interface between the conductor and the insulating layer of the multi-layered ceramic substrate.